Organic light emitting diode (OLED), as a current-type light emitting device, is applied increasingly in the high performance display field since it is characterized by spontaneous light emission, fast response, wide viewing angle, being manufacturable on a flexible substrate, etc. The OLED display device can be classified into two types in terms of the driving manner: passive matrix driving OLED (PMOLED) and active matrix driving OLED (AMOLED). The AMOLED display is likely to become a next-generation novel flat panel display in place of the liquid crystal display (LCD) due to its advantages including low manufacture cost, high response speed, power saving, direct current drive usable in a portable device, wide operating temperature range, and so on. Consequently, the AMOLED display panel is preferred by more and more people.
The AMOLED display panel generally needs to be driven by a shift signal having multiple pulses. In addition, the LCD panel also needs to be driven by a shift signal having multiple pulses such that it is sufficiently charged. However, the prior art shift register unit can only generate a shift signal having a single pulse, rather than a shift signal having multiple pulses.